Nondestructive testing is often used to characterize and detect defects in engineering materials. Two of the most common techniques used in nondestructive testing are ultrasonic inspection and eddy current inspection. Ultrasonic inspection is most commonly used for inspecting the volume of an engineering material, while eddy current inspection is predominately used for inspecting the surface of the material. Typically, in pulse-echo ultrasonic inspection, an ultrasonic transducer is moved over the surface of the engineering material and sends an ultrasound beam of energy inwards towards the material. The ultrasonic transducer receives an ultrasound beam of energy reflecting from the interior of the material. The reflected ultrasound beam of energy contain signals from the volume of the material that are represented by a discrete set of points. The discrete set of points are used to reconstruct a volumetric image of the material. The volumetric image will show defects present within the material. Typically, in driver-pickup eddy current inspection, an eddy current probe uses a drive coil to induce eddy currents within the material and a sense coil to sense secondary magnetic fields that result from the eddy currents. Signals from the secondary magnetic fields are used to generate an image showing discontinuities or flaws in the surface of the material.
Generally, ultrasonic inspection and eddy current inspection are performed independent of each other using systems dedicated to one approach or the other. Inspection of an engineering material using independent ultrasonic and eddy current systems is common because defects cannot be efficiently detected throughout the material using each method alone. For example, if a surface defect is detected by an eddy current probe and the extent of the defect within the material must be determined, then the eddy current probe must be removed and an ultrasonic transducer placed on the location that the defect was detected. Removing the eddy current probe from the material and replacing it with the ultrasonic transducer is time consuming and cumbersome. In order to overcome this problem, some nondestructive inspection systems have combined the ultrasonic transducer and the eddy current into one single unit. However, a problem with this approach is that these systems are unwieldy and unable to conform to complex shaped objects having irregular surfaces, which results in a less than thorough examination. Another problem with the combined ultrasonic and eddy current probe is that combined unit is packaged into larger and often times bulky configurations that cannot be used in tight inspection locations where separate ultrasonic and eddy current probes could be used alone. Yet another problem with the combined ultrasonic and eddy current probe is that the combined unit is packaged into rigid configurations that do not readily allow for inspection of complex curving geometries. Accordingly, there is a need for a flexible nondestructive inspection device that combines an ultrasonic transducer with an eddy current probe in a single unit, in order to inspect complex shaped objects having irregular surfaces.